Referring to FIG. 1, a conventional vehicle includes an engine 2, a generator 3 and a cooling system 1 for cooling the engine 2 and the generator 3. The engine 2 includes cylinder 21, a piston 22 that is capable of moving upwardly and downwardly in the cylinder 21, a crankshaft 23 that is driven by the piston 22, and a rotating shaft 24 that is driven by the crankshaft 23. The cooling system 1 includes a water pump 11 that is driven by the rotating shaft 24 and a heat exchanger 12 that is in fluid communication with the engine 2 and the water pump 11 so as to constitute a cooling circuit.
During the cooling process, the cooling water that flows through the engine 2 and that has been heated up by the engine 2 is transported through the water pump 11 into the heat exchanger 12 so as to be cooled down again and reflow into the engine 2 to achieve a cooling cycle.
If the generator 3 is a large-size power generating device that also provides electricity to an external electrical appliance, the generator 3 needs to be cooled down. However, the optimum working temperatures of the engine 2 and the generator 3 are different. Since the cooling system 1 includes only one water pump 11 and the heat exchanger 12 can only provide a single temperature of the cooling water, the engine 2 and the generator 3 cannot be cooled down independently. Furthermore, the water pump 11 is mechanically driven by the engine 2, and the turn-on time and the turn-off time of the water pump 11 can only be controlled by the operation time of the engine 2, so that cooling efficiency of the cooling system 1 is not optimized, thereby resulting in power loss of the engine 2 and increasing the load of the engine 2.